2 * CFQ, or complete fairness queueing, disk scheduler.
4 * Based on ideas from a previously unfinished io
5 * scheduler (round robin per-process disk scheduling) and Andrea Arcangeli.
7 * Copyright (C) 2003 Jens Axboe <axboe@kernel.dk>
9 #include <linux/module.h>
10 #include <linux/blkdev.h>
11 #include <linux/elevator.h>
12 #include <linux/jiffies.h>
13 #include <linux/rbtree.h>
14 #include <linux/ioprio.h>
15 #include <linux/blktrace_api.h>
20 /* max queue in one round of service */
21 static const int cfq_quantum
= 4;
22 static const int cfq_fifo_expire
[2] = { HZ
/ 4, HZ
/ 8 };
23 /* maximum backwards seek, in KiB */
24 static const int cfq_back_max
= 16 * 1024;
25 /* penalty of a backwards seek */
26 static const int cfq_back_penalty
= 2;
27 static const int cfq_slice_sync
= HZ
/ 10;
28 static int cfq_slice_async
= HZ
/ 25;
29 static const int cfq_slice_async_rq
= 2;
30 static int cfq_slice_idle
= HZ
/ 125;
31 static const int cfq_target_latency
= HZ
* 3/10; /* 300 ms */
32 static const int cfq_hist_divisor
= 4;
35 * offset from end of service tree
37 #define CFQ_IDLE_DELAY (HZ / 5)
40 * below this threshold, we consider thinktime immediate
42 #define CFQ_MIN_TT (2)
45 * Allow merged cfqqs to perform this amount of seeky I/O before
46 * deciding to break the queues up again.
48 #define CFQQ_COOP_TOUT (HZ)
50 #define CFQ_SLICE_SCALE (5)
51 #define CFQ_HW_QUEUE_MIN (5)
54 ((struct cfq_io_context *) (rq)->elevator_private)
55 #define RQ_CFQQ(rq) (struct cfq_queue *) ((rq)->elevator_private2)
57 static struct kmem_cache
*cfq_pool
;
58 static struct kmem_cache
*cfq_ioc_pool
;
60 static DEFINE_PER_CPU(unsigned long, cfq_ioc_count
);
61 static struct completion
*ioc_gone
;
62 static DEFINE_SPINLOCK(ioc_gone_lock
);
64 #define CFQ_PRIO_LISTS IOPRIO_BE_NR
65 #define cfq_class_idle(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_IDLE)
66 #define cfq_class_rt(cfqq) ((cfqq)->ioprio_class == IOPRIO_CLASS_RT)
68 #define sample_valid(samples) ((samples) > 80)
71 * Most of our rbtree usage is for sorting with min extraction, so
72 * if we cache the leftmost node we don't have to walk down the tree
73 * to find it. Idea borrowed from Ingo Molnars CFS scheduler. We should
74 * move this into the elevator for the rq sorting as well.
81 #define CFQ_RB_ROOT (struct cfq_rb_root) { RB_ROOT, NULL, 0, }
84 * Per process-grouping structure
89 /* various state flags, see below */
92 struct cfq_data
*cfqd
;
93 /* service_tree member */
94 struct rb_node rb_node
;
95 /* service_tree key */
97 /* prio tree member */
98 struct rb_node p_node
;
99 /* prio tree root we belong to, if any */
100 struct rb_root
*p_root
;
101 /* sorted list of pending requests */
102 struct rb_root sort_list
;
103 /* if fifo isn't expired, next request to serve */
104 struct request
*next_rq
;
105 /* requests queued in sort_list */
107 /* currently allocated requests */
109 /* fifo list of requests in sort_list */
110 struct list_head fifo
;
112 unsigned long slice_end
;
114 unsigned int slice_dispatch
;
116 /* pending metadata requests */
118 /* number of requests that are on the dispatch list or inside driver */
121 /* io prio of this group */
122 unsigned short ioprio
, org_ioprio
;
123 unsigned short ioprio_class
, org_ioprio_class
;
125 unsigned int seek_samples
;
128 sector_t last_request_pos
;
129 unsigned long seeky_start
;
133 struct cfq_rb_root
*service_tree
;
134 struct cfq_queue
*new_cfqq
;
138 * First index in the service_trees.
139 * IDLE is handled separately, so it has negative index
148 * Second index in the service_trees.
152 SYNC_NOIDLE_WORKLOAD
= 1,
158 * Per block device queue structure
161 struct request_queue
*queue
;
164 * rr lists of queues with requests, onle rr for each priority class.
165 * Counts are embedded in the cfq_rb_root
167 struct cfq_rb_root service_trees
[2][3];
168 struct cfq_rb_root service_tree_idle
;
170 * The priority currently being served
172 enum wl_prio_t serving_prio
;
173 enum wl_type_t serving_type
;
174 unsigned long workload_expires
;
177 * Each priority tree is sorted by next_request position. These
178 * trees are used when determining if two or more queues are
179 * interleaving requests (see cfq_close_cooperator).
181 struct rb_root prio_trees
[CFQ_PRIO_LISTS
];
183 unsigned int busy_queues
;
184 unsigned int busy_queues_avg
[2];
190 * queue-depth detection
195 int rq_in_driver_peak
;
198 * idle window management
200 struct timer_list idle_slice_timer
;
201 struct work_struct unplug_work
;
203 struct cfq_queue
*active_queue
;
204 struct cfq_io_context
*active_cic
;
207 * async queue for each priority case
209 struct cfq_queue
*async_cfqq
[2][IOPRIO_BE_NR
];
210 struct cfq_queue
*async_idle_cfqq
;
212 sector_t last_position
;
215 * tunables, see top of file
217 unsigned int cfq_quantum
;
218 unsigned int cfq_fifo_expire
[2];
219 unsigned int cfq_back_penalty
;
220 unsigned int cfq_back_max
;
221 unsigned int cfq_slice
[2];
222 unsigned int cfq_slice_async_rq
;
223 unsigned int cfq_slice_idle
;
224 unsigned int cfq_latency
;
226 struct list_head cic_list
;
229 * Fallback dummy cfqq for extreme OOM conditions
231 struct cfq_queue oom_cfqq
;
233 unsigned long last_end_sync_rq
;
236 static struct cfq_rb_root
*service_tree_for(enum wl_prio_t prio
,
238 struct cfq_data
*cfqd
)
240 if (prio
== IDLE_WORKLOAD
)
241 return &cfqd
->service_tree_idle
;
243 return &cfqd
->service_trees
[prio
][type
];
246 enum cfqq_state_flags
{
247 CFQ_CFQQ_FLAG_on_rr
= 0, /* on round-robin busy list */
248 CFQ_CFQQ_FLAG_wait_request
, /* waiting for a request */
249 CFQ_CFQQ_FLAG_must_dispatch
, /* must be allowed a dispatch */
250 CFQ_CFQQ_FLAG_must_alloc_slice
, /* per-slice must_alloc flag */
251 CFQ_CFQQ_FLAG_fifo_expire
, /* FIFO checked in this slice */
252 CFQ_CFQQ_FLAG_idle_window
, /* slice idling enabled */
253 CFQ_CFQQ_FLAG_prio_changed
, /* task priority has changed */
254 CFQ_CFQQ_FLAG_slice_new
, /* no requests dispatched in slice */
255 CFQ_CFQQ_FLAG_sync
, /* synchronous queue */
256 CFQ_CFQQ_FLAG_coop
, /* cfqq is shared */
259 #define CFQ_CFQQ_FNS(name) \
260 static inline void cfq_mark_cfqq_##name(struct cfq_queue *cfqq) \
262 (cfqq)->flags |= (1 << CFQ_CFQQ_FLAG_##name); \
264 static inline void cfq_clear_cfqq_##name(struct cfq_queue *cfqq) \
266 (cfqq)->flags &= ~(1 << CFQ_CFQQ_FLAG_##name); \
268 static inline int cfq_cfqq_##name(const struct cfq_queue *cfqq) \
270 return ((cfqq)->flags & (1 << CFQ_CFQQ_FLAG_##name)) != 0; \
274 CFQ_CFQQ_FNS(wait_request
);
275 CFQ_CFQQ_FNS(must_dispatch
);
276 CFQ_CFQQ_FNS(must_alloc_slice
);
277 CFQ_CFQQ_FNS(fifo_expire
);
278 CFQ_CFQQ_FNS(idle_window
);
279 CFQ_CFQQ_FNS(prio_changed
);
280 CFQ_CFQQ_FNS(slice_new
);
285 #define cfq_log_cfqq(cfqd, cfqq, fmt, args...) \
286 blk_add_trace_msg((cfqd)->queue, "cfq%d " fmt, (cfqq)->pid, ##args)
287 #define cfq_log(cfqd, fmt, args...) \
288 blk_add_trace_msg((cfqd)->queue, "cfq " fmt, ##args)
290 static inline enum wl_prio_t
cfqq_prio(struct cfq_queue
*cfqq
)
292 if (cfq_class_idle(cfqq
))
293 return IDLE_WORKLOAD
;
294 if (cfq_class_rt(cfqq
))
300 static enum wl_type_t
cfqq_type(struct cfq_queue
*cfqq
)
302 if (!cfq_cfqq_sync(cfqq
))
303 return ASYNC_WORKLOAD
;
304 if (!cfq_cfqq_idle_window(cfqq
))
305 return SYNC_NOIDLE_WORKLOAD
;
306 return SYNC_WORKLOAD
;
309 static inline int cfq_busy_queues_wl(enum wl_prio_t wl
, struct cfq_data
*cfqd
)
311 if (wl
== IDLE_WORKLOAD
)
312 return cfqd
->service_tree_idle
.count
;
314 return cfqd
->service_trees
[wl
][ASYNC_WORKLOAD
].count
315 + cfqd
->service_trees
[wl
][SYNC_NOIDLE_WORKLOAD
].count
316 + cfqd
->service_trees
[wl
][SYNC_WORKLOAD
].count
;
319 static void cfq_dispatch_insert(struct request_queue
*, struct request
*);
320 static struct cfq_queue
*cfq_get_queue(struct cfq_data
*, bool,
321 struct io_context
*, gfp_t
);
322 static struct cfq_io_context
*cfq_cic_lookup(struct cfq_data
*,
323 struct io_context
*);
325 static inline int rq_in_driver(struct cfq_data
*cfqd
)
327 return cfqd
->rq_in_driver
[0] + cfqd
->rq_in_driver
[1];
330 static inline struct cfq_queue
*cic_to_cfqq(struct cfq_io_context
*cic
,
333 return cic
->cfqq
[is_sync
];
336 static inline void cic_set_cfqq(struct cfq_io_context
*cic
,
337 struct cfq_queue
*cfqq
, bool is_sync
)
339 cic
->cfqq
[is_sync
] = cfqq
;
343 * We regard a request as SYNC, if it's either a read or has the SYNC bit
344 * set (in which case it could also be direct WRITE).
346 static inline bool cfq_bio_sync(struct bio
*bio
)
348 return bio_data_dir(bio
) == READ
|| bio_rw_flagged(bio
, BIO_RW_SYNCIO
);
352 * scheduler run of queue, if there are requests pending and no one in the
353 * driver that will restart queueing
355 static inline void cfq_schedule_dispatch(struct cfq_data
*cfqd
)
357 if (cfqd
->busy_queues
) {
358 cfq_log(cfqd
, "schedule dispatch");
359 kblockd_schedule_work(cfqd
->queue
, &cfqd
->unplug_work
);
363 static int cfq_queue_empty(struct request_queue
*q
)
365 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
367 return !cfqd
->busy_queues
;
371 * Scale schedule slice based on io priority. Use the sync time slice only
372 * if a queue is marked sync and has sync io queued. A sync queue with async
373 * io only, should not get full sync slice length.
375 static inline int cfq_prio_slice(struct cfq_data
*cfqd
, bool sync
,
378 const int base_slice
= cfqd
->cfq_slice
[sync
];
380 WARN_ON(prio
>= IOPRIO_BE_NR
);
382 return base_slice
+ (base_slice
/CFQ_SLICE_SCALE
* (4 - prio
));
386 cfq_prio_to_slice(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
388 return cfq_prio_slice(cfqd
, cfq_cfqq_sync(cfqq
), cfqq
->ioprio
);
392 * get averaged number of queues of RT/BE priority.
393 * average is updated, with a formula that gives more weight to higher numbers,
394 * to quickly follows sudden increases and decrease slowly
397 static inline unsigned cfq_get_avg_queues(struct cfq_data
*cfqd
, bool rt
)
399 unsigned min_q
, max_q
;
400 unsigned mult
= cfq_hist_divisor
- 1;
401 unsigned round
= cfq_hist_divisor
/ 2;
402 unsigned busy
= cfq_busy_queues_wl(rt
, cfqd
);
404 min_q
= min(cfqd
->busy_queues_avg
[rt
], busy
);
405 max_q
= max(cfqd
->busy_queues_avg
[rt
], busy
);
406 cfqd
->busy_queues_avg
[rt
] = (mult
* max_q
+ min_q
+ round
) /
408 return cfqd
->busy_queues_avg
[rt
];
412 cfq_set_prio_slice(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
414 unsigned slice
= cfq_prio_to_slice(cfqd
, cfqq
);
415 if (cfqd
->cfq_latency
) {
416 /* interested queues (we consider only the ones with the same
418 unsigned iq
= cfq_get_avg_queues(cfqd
, cfq_class_rt(cfqq
));
419 unsigned sync_slice
= cfqd
->cfq_slice
[1];
420 unsigned expect_latency
= sync_slice
* iq
;
421 if (expect_latency
> cfq_target_latency
) {
422 unsigned base_low_slice
= 2 * cfqd
->cfq_slice_idle
;
423 /* scale low_slice according to IO priority
424 * and sync vs async */
426 min(slice
, base_low_slice
* slice
/ sync_slice
);
427 /* the adapted slice value is scaled to fit all iqs
428 * into the target latency */
429 slice
= max(slice
* cfq_target_latency
/ expect_latency
,
433 cfqq
->slice_end
= jiffies
+ slice
;
434 cfq_log_cfqq(cfqd
, cfqq
, "set_slice=%lu", cfqq
->slice_end
- jiffies
);
438 * We need to wrap this check in cfq_cfqq_slice_new(), since ->slice_end
439 * isn't valid until the first request from the dispatch is activated
440 * and the slice time set.
442 static inline bool cfq_slice_used(struct cfq_queue
*cfqq
)
444 if (cfq_cfqq_slice_new(cfqq
))
446 if (time_before(jiffies
, cfqq
->slice_end
))
453 * Lifted from AS - choose which of rq1 and rq2 that is best served now.
454 * We choose the request that is closest to the head right now. Distance
455 * behind the head is penalized and only allowed to a certain extent.
457 static struct request
*
458 cfq_choose_req(struct cfq_data
*cfqd
, struct request
*rq1
, struct request
*rq2
, sector_t last
)
460 sector_t s1
, s2
, d1
= 0, d2
= 0;
461 unsigned long back_max
;
462 #define CFQ_RQ1_WRAP 0x01 /* request 1 wraps */
463 #define CFQ_RQ2_WRAP 0x02 /* request 2 wraps */
464 unsigned wrap
= 0; /* bit mask: requests behind the disk head? */
466 if (rq1
== NULL
|| rq1
== rq2
)
471 if (rq_is_sync(rq1
) && !rq_is_sync(rq2
))
473 else if (rq_is_sync(rq2
) && !rq_is_sync(rq1
))
475 if (rq_is_meta(rq1
) && !rq_is_meta(rq2
))
477 else if (rq_is_meta(rq2
) && !rq_is_meta(rq1
))
480 s1
= blk_rq_pos(rq1
);
481 s2
= blk_rq_pos(rq2
);
484 * by definition, 1KiB is 2 sectors
486 back_max
= cfqd
->cfq_back_max
* 2;
489 * Strict one way elevator _except_ in the case where we allow
490 * short backward seeks which are biased as twice the cost of a
491 * similar forward seek.
495 else if (s1
+ back_max
>= last
)
496 d1
= (last
- s1
) * cfqd
->cfq_back_penalty
;
498 wrap
|= CFQ_RQ1_WRAP
;
502 else if (s2
+ back_max
>= last
)
503 d2
= (last
- s2
) * cfqd
->cfq_back_penalty
;
505 wrap
|= CFQ_RQ2_WRAP
;
507 /* Found required data */
510 * By doing switch() on the bit mask "wrap" we avoid having to
511 * check two variables for all permutations: --> faster!
514 case 0: /* common case for CFQ: rq1 and rq2 not wrapped */
530 case (CFQ_RQ1_WRAP
|CFQ_RQ2_WRAP
): /* both rqs wrapped */
533 * Since both rqs are wrapped,
534 * start with the one that's further behind head
535 * (--> only *one* back seek required),
536 * since back seek takes more time than forward.
546 * The below is leftmost cache rbtree addon
548 static struct cfq_queue
*cfq_rb_first(struct cfq_rb_root
*root
)
551 root
->left
= rb_first(&root
->rb
);
554 return rb_entry(root
->left
, struct cfq_queue
, rb_node
);
559 static void rb_erase_init(struct rb_node
*n
, struct rb_root
*root
)
565 static void cfq_rb_erase(struct rb_node
*n
, struct cfq_rb_root
*root
)
569 rb_erase_init(n
, &root
->rb
);
574 * would be nice to take fifo expire time into account as well
576 static struct request
*
577 cfq_find_next_rq(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
,
578 struct request
*last
)
580 struct rb_node
*rbnext
= rb_next(&last
->rb_node
);
581 struct rb_node
*rbprev
= rb_prev(&last
->rb_node
);
582 struct request
*next
= NULL
, *prev
= NULL
;
584 BUG_ON(RB_EMPTY_NODE(&last
->rb_node
));
587 prev
= rb_entry_rq(rbprev
);
590 next
= rb_entry_rq(rbnext
);
592 rbnext
= rb_first(&cfqq
->sort_list
);
593 if (rbnext
&& rbnext
!= &last
->rb_node
)
594 next
= rb_entry_rq(rbnext
);
597 return cfq_choose_req(cfqd
, next
, prev
, blk_rq_pos(last
));
600 static unsigned long cfq_slice_offset(struct cfq_data
*cfqd
,
601 struct cfq_queue
*cfqq
)
604 * just an approximation, should be ok.
606 return (cfqd
->busy_queues
- 1) * (cfq_prio_slice(cfqd
, 1, 0) -
607 cfq_prio_slice(cfqd
, cfq_cfqq_sync(cfqq
), cfqq
->ioprio
));
611 * The cfqd->service_trees holds all pending cfq_queue's that have
612 * requests waiting to be processed. It is sorted in the order that
613 * we will service the queues.
615 static void cfq_service_tree_add(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
,
618 struct rb_node
**p
, *parent
;
619 struct cfq_queue
*__cfqq
;
620 unsigned long rb_key
;
621 struct cfq_rb_root
*service_tree
;
624 service_tree
= service_tree_for(cfqq_prio(cfqq
), cfqq_type(cfqq
), cfqd
);
625 if (cfq_class_idle(cfqq
)) {
626 rb_key
= CFQ_IDLE_DELAY
;
627 parent
= rb_last(&service_tree
->rb
);
628 if (parent
&& parent
!= &cfqq
->rb_node
) {
629 __cfqq
= rb_entry(parent
, struct cfq_queue
, rb_node
);
630 rb_key
+= __cfqq
->rb_key
;
633 } else if (!add_front
) {
635 * Get our rb key offset. Subtract any residual slice
636 * value carried from last service. A negative resid
637 * count indicates slice overrun, and this should position
638 * the next service time further away in the tree.
640 rb_key
= cfq_slice_offset(cfqd
, cfqq
) + jiffies
;
641 rb_key
-= cfqq
->slice_resid
;
642 cfqq
->slice_resid
= 0;
645 __cfqq
= cfq_rb_first(service_tree
);
646 rb_key
+= __cfqq
? __cfqq
->rb_key
: jiffies
;
649 if (!RB_EMPTY_NODE(&cfqq
->rb_node
)) {
651 * same position, nothing more to do
653 if (rb_key
== cfqq
->rb_key
&&
654 cfqq
->service_tree
== service_tree
)
657 cfq_rb_erase(&cfqq
->rb_node
, cfqq
->service_tree
);
658 cfqq
->service_tree
= NULL
;
663 cfqq
->service_tree
= service_tree
;
664 p
= &service_tree
->rb
.rb_node
;
669 __cfqq
= rb_entry(parent
, struct cfq_queue
, rb_node
);
672 * sort by key, that represents service time.
674 if (time_before(rb_key
, __cfqq
->rb_key
))
685 service_tree
->left
= &cfqq
->rb_node
;
687 cfqq
->rb_key
= rb_key
;
688 rb_link_node(&cfqq
->rb_node
, parent
, p
);
689 rb_insert_color(&cfqq
->rb_node
, &service_tree
->rb
);
690 service_tree
->count
++;
693 static struct cfq_queue
*
694 cfq_prio_tree_lookup(struct cfq_data
*cfqd
, struct rb_root
*root
,
695 sector_t sector
, struct rb_node
**ret_parent
,
696 struct rb_node
***rb_link
)
698 struct rb_node
**p
, *parent
;
699 struct cfq_queue
*cfqq
= NULL
;
707 cfqq
= rb_entry(parent
, struct cfq_queue
, p_node
);
710 * Sort strictly based on sector. Smallest to the left,
711 * largest to the right.
713 if (sector
> blk_rq_pos(cfqq
->next_rq
))
715 else if (sector
< blk_rq_pos(cfqq
->next_rq
))
723 *ret_parent
= parent
;
729 static void cfq_prio_tree_add(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
731 struct rb_node
**p
, *parent
;
732 struct cfq_queue
*__cfqq
;
735 rb_erase(&cfqq
->p_node
, cfqq
->p_root
);
739 if (cfq_class_idle(cfqq
))
744 cfqq
->p_root
= &cfqd
->prio_trees
[cfqq
->org_ioprio
];
745 __cfqq
= cfq_prio_tree_lookup(cfqd
, cfqq
->p_root
,
746 blk_rq_pos(cfqq
->next_rq
), &parent
, &p
);
748 rb_link_node(&cfqq
->p_node
, parent
, p
);
749 rb_insert_color(&cfqq
->p_node
, cfqq
->p_root
);
755 * Update cfqq's position in the service tree.
757 static void cfq_resort_rr_list(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
760 * Resorting requires the cfqq to be on the RR list already.
762 if (cfq_cfqq_on_rr(cfqq
)) {
763 cfq_service_tree_add(cfqd
, cfqq
, 0);
764 cfq_prio_tree_add(cfqd
, cfqq
);
769 * add to busy list of queues for service, trying to be fair in ordering
770 * the pending list according to last request service
772 static void cfq_add_cfqq_rr(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
774 cfq_log_cfqq(cfqd
, cfqq
, "add_to_rr");
775 BUG_ON(cfq_cfqq_on_rr(cfqq
));
776 cfq_mark_cfqq_on_rr(cfqq
);
779 cfq_resort_rr_list(cfqd
, cfqq
);
783 * Called when the cfqq no longer has requests pending, remove it from
786 static void cfq_del_cfqq_rr(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
788 cfq_log_cfqq(cfqd
, cfqq
, "del_from_rr");
789 BUG_ON(!cfq_cfqq_on_rr(cfqq
));
790 cfq_clear_cfqq_on_rr(cfqq
);
792 if (!RB_EMPTY_NODE(&cfqq
->rb_node
)) {
793 cfq_rb_erase(&cfqq
->rb_node
, cfqq
->service_tree
);
794 cfqq
->service_tree
= NULL
;
797 rb_erase(&cfqq
->p_node
, cfqq
->p_root
);
801 BUG_ON(!cfqd
->busy_queues
);
806 * rb tree support functions
808 static void cfq_del_rq_rb(struct request
*rq
)
810 struct cfq_queue
*cfqq
= RQ_CFQQ(rq
);
811 struct cfq_data
*cfqd
= cfqq
->cfqd
;
812 const int sync
= rq_is_sync(rq
);
814 BUG_ON(!cfqq
->queued
[sync
]);
815 cfqq
->queued
[sync
]--;
817 elv_rb_del(&cfqq
->sort_list
, rq
);
819 if (cfq_cfqq_on_rr(cfqq
) && RB_EMPTY_ROOT(&cfqq
->sort_list
))
820 cfq_del_cfqq_rr(cfqd
, cfqq
);
823 static void cfq_add_rq_rb(struct request
*rq
)
825 struct cfq_queue
*cfqq
= RQ_CFQQ(rq
);
826 struct cfq_data
*cfqd
= cfqq
->cfqd
;
827 struct request
*__alias
, *prev
;
829 cfqq
->queued
[rq_is_sync(rq
)]++;
832 * looks a little odd, but the first insert might return an alias.
833 * if that happens, put the alias on the dispatch list
835 while ((__alias
= elv_rb_add(&cfqq
->sort_list
, rq
)) != NULL
)
836 cfq_dispatch_insert(cfqd
->queue
, __alias
);
838 if (!cfq_cfqq_on_rr(cfqq
))
839 cfq_add_cfqq_rr(cfqd
, cfqq
);
842 * check if this request is a better next-serve candidate
844 prev
= cfqq
->next_rq
;
845 cfqq
->next_rq
= cfq_choose_req(cfqd
, cfqq
->next_rq
, rq
, cfqd
->last_position
);
848 * adjust priority tree position, if ->next_rq changes
850 if (prev
!= cfqq
->next_rq
)
851 cfq_prio_tree_add(cfqd
, cfqq
);
853 BUG_ON(!cfqq
->next_rq
);
856 static void cfq_reposition_rq_rb(struct cfq_queue
*cfqq
, struct request
*rq
)
858 elv_rb_del(&cfqq
->sort_list
, rq
);
859 cfqq
->queued
[rq_is_sync(rq
)]--;
863 static struct request
*
864 cfq_find_rq_fmerge(struct cfq_data
*cfqd
, struct bio
*bio
)
866 struct task_struct
*tsk
= current
;
867 struct cfq_io_context
*cic
;
868 struct cfq_queue
*cfqq
;
870 cic
= cfq_cic_lookup(cfqd
, tsk
->io_context
);
874 cfqq
= cic_to_cfqq(cic
, cfq_bio_sync(bio
));
876 sector_t sector
= bio
->bi_sector
+ bio_sectors(bio
);
878 return elv_rb_find(&cfqq
->sort_list
, sector
);
884 static void cfq_activate_request(struct request_queue
*q
, struct request
*rq
)
886 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
888 cfqd
->rq_in_driver
[rq_is_sync(rq
)]++;
889 cfq_log_cfqq(cfqd
, RQ_CFQQ(rq
), "activate rq, drv=%d",
892 cfqd
->last_position
= blk_rq_pos(rq
) + blk_rq_sectors(rq
);
895 static void cfq_deactivate_request(struct request_queue
*q
, struct request
*rq
)
897 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
898 const int sync
= rq_is_sync(rq
);
900 WARN_ON(!cfqd
->rq_in_driver
[sync
]);
901 cfqd
->rq_in_driver
[sync
]--;
902 cfq_log_cfqq(cfqd
, RQ_CFQQ(rq
), "deactivate rq, drv=%d",
906 static void cfq_remove_request(struct request
*rq
)
908 struct cfq_queue
*cfqq
= RQ_CFQQ(rq
);
910 if (cfqq
->next_rq
== rq
)
911 cfqq
->next_rq
= cfq_find_next_rq(cfqq
->cfqd
, cfqq
, rq
);
913 list_del_init(&rq
->queuelist
);
916 cfqq
->cfqd
->rq_queued
--;
917 if (rq_is_meta(rq
)) {
918 WARN_ON(!cfqq
->meta_pending
);
919 cfqq
->meta_pending
--;
923 static int cfq_merge(struct request_queue
*q
, struct request
**req
,
926 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
927 struct request
*__rq
;
929 __rq
= cfq_find_rq_fmerge(cfqd
, bio
);
930 if (__rq
&& elv_rq_merge_ok(__rq
, bio
)) {
932 return ELEVATOR_FRONT_MERGE
;
935 return ELEVATOR_NO_MERGE
;
938 static void cfq_merged_request(struct request_queue
*q
, struct request
*req
,
941 if (type
== ELEVATOR_FRONT_MERGE
) {
942 struct cfq_queue
*cfqq
= RQ_CFQQ(req
);
944 cfq_reposition_rq_rb(cfqq
, req
);
949 cfq_merged_requests(struct request_queue
*q
, struct request
*rq
,
950 struct request
*next
)
952 struct cfq_queue
*cfqq
= RQ_CFQQ(rq
);
954 * reposition in fifo if next is older than rq
956 if (!list_empty(&rq
->queuelist
) && !list_empty(&next
->queuelist
) &&
957 time_before(rq_fifo_time(next
), rq_fifo_time(rq
))) {
958 list_move(&rq
->queuelist
, &next
->queuelist
);
959 rq_set_fifo_time(rq
, rq_fifo_time(next
));
962 if (cfqq
->next_rq
== next
)
964 cfq_remove_request(next
);
967 static int cfq_allow_merge(struct request_queue
*q
, struct request
*rq
,
970 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
971 struct cfq_io_context
*cic
;
972 struct cfq_queue
*cfqq
;
975 * Disallow merge of a sync bio into an async request.
977 if (cfq_bio_sync(bio
) && !rq_is_sync(rq
))
981 * Lookup the cfqq that this bio will be queued with. Allow
982 * merge only if rq is queued there.
984 cic
= cfq_cic_lookup(cfqd
, current
->io_context
);
988 cfqq
= cic_to_cfqq(cic
, cfq_bio_sync(bio
));
989 return cfqq
== RQ_CFQQ(rq
);
992 static void __cfq_set_active_queue(struct cfq_data
*cfqd
,
993 struct cfq_queue
*cfqq
)
996 cfq_log_cfqq(cfqd
, cfqq
, "set_active");
998 cfqq
->slice_dispatch
= 0;
1000 cfq_clear_cfqq_wait_request(cfqq
);
1001 cfq_clear_cfqq_must_dispatch(cfqq
);
1002 cfq_clear_cfqq_must_alloc_slice(cfqq
);
1003 cfq_clear_cfqq_fifo_expire(cfqq
);
1004 cfq_mark_cfqq_slice_new(cfqq
);
1006 del_timer(&cfqd
->idle_slice_timer
);
1009 cfqd
->active_queue
= cfqq
;
1013 * current cfqq expired its slice (or was too idle), select new one
1016 __cfq_slice_expired(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
,
1019 cfq_log_cfqq(cfqd
, cfqq
, "slice expired t=%d", timed_out
);
1021 if (cfq_cfqq_wait_request(cfqq
))
1022 del_timer(&cfqd
->idle_slice_timer
);
1024 cfq_clear_cfqq_wait_request(cfqq
);
1027 * store what was left of this slice, if the queue idled/timed out
1029 if (timed_out
&& !cfq_cfqq_slice_new(cfqq
)) {
1030 cfqq
->slice_resid
= cfqq
->slice_end
- jiffies
;
1031 cfq_log_cfqq(cfqd
, cfqq
, "resid=%ld", cfqq
->slice_resid
);
1034 cfq_resort_rr_list(cfqd
, cfqq
);
1036 if (cfqq
== cfqd
->active_queue
)
1037 cfqd
->active_queue
= NULL
;
1039 if (cfqd
->active_cic
) {
1040 put_io_context(cfqd
->active_cic
->ioc
);
1041 cfqd
->active_cic
= NULL
;
1045 static inline void cfq_slice_expired(struct cfq_data
*cfqd
, bool timed_out
)
1047 struct cfq_queue
*cfqq
= cfqd
->active_queue
;
1050 __cfq_slice_expired(cfqd
, cfqq
, timed_out
);
1054 * Get next queue for service. Unless we have a queue preemption,
1055 * we'll simply select the first cfqq in the service tree.
1057 static struct cfq_queue
*cfq_get_next_queue(struct cfq_data
*cfqd
)
1059 struct cfq_rb_root
*service_tree
=
1060 service_tree_for(cfqd
->serving_prio
, cfqd
->serving_type
, cfqd
);
1062 if (RB_EMPTY_ROOT(&service_tree
->rb
))
1064 return cfq_rb_first(service_tree
);
1068 * Get and set a new active queue for service.
1070 static struct cfq_queue
*cfq_set_active_queue(struct cfq_data
*cfqd
,
1071 struct cfq_queue
*cfqq
)
1074 cfqq
= cfq_get_next_queue(cfqd
);
1076 __cfq_set_active_queue(cfqd
, cfqq
);
1080 static inline sector_t
cfq_dist_from_last(struct cfq_data
*cfqd
,
1083 if (blk_rq_pos(rq
) >= cfqd
->last_position
)
1084 return blk_rq_pos(rq
) - cfqd
->last_position
;
1086 return cfqd
->last_position
- blk_rq_pos(rq
);
1089 #define CFQQ_SEEK_THR 8 * 1024
1090 #define CFQQ_SEEKY(cfqq) ((cfqq)->seek_mean > CFQQ_SEEK_THR)
1092 static inline int cfq_rq_close(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
,
1095 sector_t sdist
= cfqq
->seek_mean
;
1097 if (!sample_valid(cfqq
->seek_samples
))
1098 sdist
= CFQQ_SEEK_THR
;
1100 return cfq_dist_from_last(cfqd
, rq
) <= sdist
;
1103 static struct cfq_queue
*cfqq_close(struct cfq_data
*cfqd
,
1104 struct cfq_queue
*cur_cfqq
)
1106 struct rb_root
*root
= &cfqd
->prio_trees
[cur_cfqq
->org_ioprio
];
1107 struct rb_node
*parent
, *node
;
1108 struct cfq_queue
*__cfqq
;
1109 sector_t sector
= cfqd
->last_position
;
1111 if (RB_EMPTY_ROOT(root
))
1115 * First, if we find a request starting at the end of the last
1116 * request, choose it.
1118 __cfqq
= cfq_prio_tree_lookup(cfqd
, root
, sector
, &parent
, NULL
);
1123 * If the exact sector wasn't found, the parent of the NULL leaf
1124 * will contain the closest sector.
1126 __cfqq
= rb_entry(parent
, struct cfq_queue
, p_node
);
1127 if (cfq_rq_close(cfqd
, cur_cfqq
, __cfqq
->next_rq
))
1130 if (blk_rq_pos(__cfqq
->next_rq
) < sector
)
1131 node
= rb_next(&__cfqq
->p_node
);
1133 node
= rb_prev(&__cfqq
->p_node
);
1137 __cfqq
= rb_entry(node
, struct cfq_queue
, p_node
);
1138 if (cfq_rq_close(cfqd
, cur_cfqq
, __cfqq
->next_rq
))
1146 * cur_cfqq - passed in so that we don't decide that the current queue is
1147 * closely cooperating with itself.
1149 * So, basically we're assuming that that cur_cfqq has dispatched at least
1150 * one request, and that cfqd->last_position reflects a position on the disk
1151 * associated with the I/O issued by cur_cfqq. I'm not sure this is a valid
1154 static struct cfq_queue
*cfq_close_cooperator(struct cfq_data
*cfqd
,
1155 struct cfq_queue
*cur_cfqq
)
1157 struct cfq_queue
*cfqq
;
1159 if (!cfq_cfqq_sync(cur_cfqq
))
1161 if (CFQQ_SEEKY(cur_cfqq
))
1165 * We should notice if some of the queues are cooperating, eg
1166 * working closely on the same area of the disk. In that case,
1167 * we can group them together and don't waste time idling.
1169 cfqq
= cfqq_close(cfqd
, cur_cfqq
);
1174 * It only makes sense to merge sync queues.
1176 if (!cfq_cfqq_sync(cfqq
))
1178 if (CFQQ_SEEKY(cfqq
))
1182 * Do not merge queues of different priority classes
1184 if (cfq_class_rt(cfqq
) != cfq_class_rt(cur_cfqq
))
1191 * Determine whether we should enforce idle window for this queue.
1194 static bool cfq_should_idle(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
1196 enum wl_prio_t prio
= cfqq_prio(cfqq
);
1197 struct cfq_rb_root
*service_tree
= cfqq
->service_tree
;
1199 /* We never do for idle class queues. */
1200 if (prio
== IDLE_WORKLOAD
)
1203 /* We do for queues that were marked with idle window flag. */
1204 if (cfq_cfqq_idle_window(cfqq
))
1208 * Otherwise, we do only if they are the last ones
1209 * in their service tree.
1212 service_tree
= service_tree_for(prio
, cfqq_type(cfqq
), cfqd
);
1214 if (service_tree
->count
== 0)
1217 return (service_tree
->count
== 1 && cfq_rb_first(service_tree
) == cfqq
);
1220 static void cfq_arm_slice_timer(struct cfq_data
*cfqd
)
1222 struct cfq_queue
*cfqq
= cfqd
->active_queue
;
1223 struct cfq_io_context
*cic
;
1227 * SSD device without seek penalty, disable idling. But only do so
1228 * for devices that support queuing, otherwise we still have a problem
1229 * with sync vs async workloads.
1231 if (blk_queue_nonrot(cfqd
->queue
) && cfqd
->hw_tag
)
1234 WARN_ON(!RB_EMPTY_ROOT(&cfqq
->sort_list
));
1235 WARN_ON(cfq_cfqq_slice_new(cfqq
));
1238 * idle is disabled, either manually or by past process history
1240 if (!cfqd
->cfq_slice_idle
|| !cfq_should_idle(cfqd
, cfqq
))
1244 * still requests with the driver, don't idle
1246 if (rq_in_driver(cfqd
))
1250 * task has exited, don't wait
1252 cic
= cfqd
->active_cic
;
1253 if (!cic
|| !atomic_read(&cic
->ioc
->nr_tasks
))
1257 * If our average think time is larger than the remaining time
1258 * slice, then don't idle. This avoids overrunning the allotted
1261 if (sample_valid(cic
->ttime_samples
) &&
1262 (cfqq
->slice_end
- jiffies
< cic
->ttime_mean
))
1265 cfq_mark_cfqq_wait_request(cfqq
);
1267 sl
= cfqd
->cfq_slice_idle
;
1268 /* are we servicing noidle tree, and there are more queues?
1269 * non-rotational or NCQ: no idle
1270 * non-NCQ rotational : very small idle, to allow
1271 * fair distribution of slice time for a process doing back-to-back
1274 if (cfqd
->serving_type
== SYNC_NOIDLE_WORKLOAD
&&
1275 service_tree_for(cfqd
->serving_prio
, SYNC_NOIDLE_WORKLOAD
, cfqd
)
1277 if (blk_queue_nonrot(cfqd
->queue
) || cfqd
->hw_tag
)
1279 sl
= min(sl
, msecs_to_jiffies(CFQ_MIN_TT
));
1282 mod_timer(&cfqd
->idle_slice_timer
, jiffies
+ sl
);
1283 cfq_log_cfqq(cfqd
, cfqq
, "arm_idle: %lu", sl
);
1287 * Move request from internal lists to the request queue dispatch list.
1289 static void cfq_dispatch_insert(struct request_queue
*q
, struct request
*rq
)
1291 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
1292 struct cfq_queue
*cfqq
= RQ_CFQQ(rq
);
1294 cfq_log_cfqq(cfqd
, cfqq
, "dispatch_insert");
1296 cfqq
->next_rq
= cfq_find_next_rq(cfqd
, cfqq
, rq
);
1297 cfq_remove_request(rq
);
1299 elv_dispatch_sort(q
, rq
);
1301 if (cfq_cfqq_sync(cfqq
))
1302 cfqd
->sync_flight
++;
1306 * return expired entry, or NULL to just start from scratch in rbtree
1308 static struct request
*cfq_check_fifo(struct cfq_queue
*cfqq
)
1310 struct request
*rq
= NULL
;
1312 if (cfq_cfqq_fifo_expire(cfqq
))
1315 cfq_mark_cfqq_fifo_expire(cfqq
);
1317 if (list_empty(&cfqq
->fifo
))
1320 rq
= rq_entry_fifo(cfqq
->fifo
.next
);
1321 if (time_before(jiffies
, rq_fifo_time(rq
)))
1324 cfq_log_cfqq(cfqq
->cfqd
, cfqq
, "fifo=%p", rq
);
1329 cfq_prio_to_maxrq(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
1331 const int base_rq
= cfqd
->cfq_slice_async_rq
;
1333 WARN_ON(cfqq
->ioprio
>= IOPRIO_BE_NR
);
1335 return 2 * (base_rq
+ base_rq
* (CFQ_PRIO_LISTS
- 1 - cfqq
->ioprio
));
1339 * Must be called with the queue_lock held.
1341 static int cfqq_process_refs(struct cfq_queue
*cfqq
)
1343 int process_refs
, io_refs
;
1345 io_refs
= cfqq
->allocated
[READ
] + cfqq
->allocated
[WRITE
];
1346 process_refs
= atomic_read(&cfqq
->ref
) - io_refs
;
1347 BUG_ON(process_refs
< 0);
1348 return process_refs
;
1351 static void cfq_setup_merge(struct cfq_queue
*cfqq
, struct cfq_queue
*new_cfqq
)
1353 int process_refs
, new_process_refs
;
1354 struct cfq_queue
*__cfqq
;
1356 /* Avoid a circular list and skip interim queue merges */
1357 while ((__cfqq
= new_cfqq
->new_cfqq
)) {
1363 process_refs
= cfqq_process_refs(cfqq
);
1365 * If the process for the cfqq has gone away, there is no
1366 * sense in merging the queues.
1368 if (process_refs
== 0)
1372 * Merge in the direction of the lesser amount of work.
1374 new_process_refs
= cfqq_process_refs(new_cfqq
);
1375 if (new_process_refs
>= process_refs
) {
1376 cfqq
->new_cfqq
= new_cfqq
;
1377 atomic_add(process_refs
, &new_cfqq
->ref
);
1379 new_cfqq
->new_cfqq
= cfqq
;
1380 atomic_add(new_process_refs
, &cfqq
->ref
);
1384 static enum wl_type_t
cfq_choose_wl(struct cfq_data
*cfqd
, enum wl_prio_t prio
,
1387 struct cfq_queue
*queue
;
1389 bool key_valid
= false;
1390 unsigned long lowest_key
= 0;
1391 enum wl_type_t cur_best
= SYNC_NOIDLE_WORKLOAD
;
1395 * When priorities switched, we prefer starting
1396 * from SYNC_NOIDLE (first choice), or just SYNC
1399 if (service_tree_for(prio
, cur_best
, cfqd
)->count
)
1401 cur_best
= SYNC_WORKLOAD
;
1402 if (service_tree_for(prio
, cur_best
, cfqd
)->count
)
1405 return ASYNC_WORKLOAD
;
1408 for (i
= 0; i
< 3; ++i
) {
1409 /* otherwise, select the one with lowest rb_key */
1410 queue
= cfq_rb_first(service_tree_for(prio
, i
, cfqd
));
1412 (!key_valid
|| time_before(queue
->rb_key
, lowest_key
))) {
1413 lowest_key
= queue
->rb_key
;
1422 static void choose_service_tree(struct cfq_data
*cfqd
)
1424 enum wl_prio_t previous_prio
= cfqd
->serving_prio
;
1429 /* Choose next priority. RT > BE > IDLE */
1430 if (cfq_busy_queues_wl(RT_WORKLOAD
, cfqd
))
1431 cfqd
->serving_prio
= RT_WORKLOAD
;
1432 else if (cfq_busy_queues_wl(BE_WORKLOAD
, cfqd
))
1433 cfqd
->serving_prio
= BE_WORKLOAD
;
1435 cfqd
->serving_prio
= IDLE_WORKLOAD
;
1436 cfqd
->workload_expires
= jiffies
+ 1;
1441 * For RT and BE, we have to choose also the type
1442 * (SYNC, SYNC_NOIDLE, ASYNC), and to compute a workload
1445 prio_changed
= (cfqd
->serving_prio
!= previous_prio
);
1446 count
= service_tree_for(cfqd
->serving_prio
, cfqd
->serving_type
, cfqd
)
1450 * If priority didn't change, check workload expiration,
1451 * and that we still have other queues ready
1453 if (!prio_changed
&& count
&&
1454 !time_after(jiffies
, cfqd
->workload_expires
))
1457 /* otherwise select new workload type */
1458 cfqd
->serving_type
=
1459 cfq_choose_wl(cfqd
, cfqd
->serving_prio
, prio_changed
);
1460 count
= service_tree_for(cfqd
->serving_prio
, cfqd
->serving_type
, cfqd
)
1464 * the workload slice is computed as a fraction of target latency
1465 * proportional to the number of queues in that workload, over
1466 * all the queues in the same priority class
1468 slice
= cfq_target_latency
* count
/
1469 max_t(unsigned, cfqd
->busy_queues_avg
[cfqd
->serving_prio
],
1470 cfq_busy_queues_wl(cfqd
->serving_prio
, cfqd
));
1472 if (cfqd
->serving_type
== ASYNC_WORKLOAD
)
1473 /* async workload slice is scaled down according to
1474 * the sync/async slice ratio. */
1475 slice
= slice
* cfqd
->cfq_slice
[0] / cfqd
->cfq_slice
[1];
1477 /* sync workload slice is at least 2 * cfq_slice_idle */
1478 slice
= max(slice
, 2 * cfqd
->cfq_slice_idle
);
1480 slice
= max_t(unsigned, slice
, CFQ_MIN_TT
);
1481 cfqd
->workload_expires
= jiffies
+ slice
;
1485 * Select a queue for service. If we have a current active queue,
1486 * check whether to continue servicing it, or retrieve and set a new one.
1488 static struct cfq_queue
*cfq_select_queue(struct cfq_data
*cfqd
)
1490 struct cfq_queue
*cfqq
, *new_cfqq
= NULL
;
1492 cfqq
= cfqd
->active_queue
;
1497 * The active queue has run out of time, expire it and select new.
1499 if (cfq_slice_used(cfqq
) && !cfq_cfqq_must_dispatch(cfqq
))
1503 * The active queue has requests and isn't expired, allow it to
1506 if (!RB_EMPTY_ROOT(&cfqq
->sort_list
))
1510 * If another queue has a request waiting within our mean seek
1511 * distance, let it run. The expire code will check for close
1512 * cooperators and put the close queue at the front of the service
1513 * tree. If possible, merge the expiring queue with the new cfqq.
1515 new_cfqq
= cfq_close_cooperator(cfqd
, cfqq
);
1517 if (!cfqq
->new_cfqq
)
1518 cfq_setup_merge(cfqq
, new_cfqq
);
1523 * No requests pending. If the active queue still has requests in
1524 * flight or is idling for a new request, allow either of these
1525 * conditions to happen (or time out) before selecting a new queue.
1527 if (timer_pending(&cfqd
->idle_slice_timer
) ||
1528 (cfqq
->dispatched
&& cfq_should_idle(cfqd
, cfqq
))) {
1534 cfq_slice_expired(cfqd
, 0);
1537 * Current queue expired. Check if we have to switch to a new
1541 choose_service_tree(cfqd
);
1543 cfqq
= cfq_set_active_queue(cfqd
, new_cfqq
);
1548 static int __cfq_forced_dispatch_cfqq(struct cfq_queue
*cfqq
)
1552 while (cfqq
->next_rq
) {
1553 cfq_dispatch_insert(cfqq
->cfqd
->queue
, cfqq
->next_rq
);
1557 BUG_ON(!list_empty(&cfqq
->fifo
));
1562 * Drain our current requests. Used for barriers and when switching
1563 * io schedulers on-the-fly.
1565 static int cfq_forced_dispatch(struct cfq_data
*cfqd
)
1567 struct cfq_queue
*cfqq
;
1570 for (i
= 0; i
< 2; ++i
)
1571 for (j
= 0; j
< 3; ++j
)
1572 while ((cfqq
= cfq_rb_first(&cfqd
->service_trees
[i
][j
]))
1574 dispatched
+= __cfq_forced_dispatch_cfqq(cfqq
);
1576 while ((cfqq
= cfq_rb_first(&cfqd
->service_tree_idle
)) != NULL
)
1577 dispatched
+= __cfq_forced_dispatch_cfqq(cfqq
);
1579 cfq_slice_expired(cfqd
, 0);
1581 BUG_ON(cfqd
->busy_queues
);
1583 cfq_log(cfqd
, "forced_dispatch=%d", dispatched
);
1587 static bool cfq_may_dispatch(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
1589 unsigned int max_dispatch
;
1592 * Drain async requests before we start sync IO
1594 if (cfq_should_idle(cfqd
, cfqq
) && cfqd
->rq_in_driver
[BLK_RW_ASYNC
])
1598 * If this is an async queue and we have sync IO in flight, let it wait
1600 if (cfqd
->sync_flight
&& !cfq_cfqq_sync(cfqq
))
1603 max_dispatch
= cfqd
->cfq_quantum
;
1604 if (cfq_class_idle(cfqq
))
1608 * Does this cfqq already have too much IO in flight?
1610 if (cfqq
->dispatched
>= max_dispatch
) {
1612 * idle queue must always only have a single IO in flight
1614 if (cfq_class_idle(cfqq
))
1618 * We have other queues, don't allow more IO from this one
1620 if (cfqd
->busy_queues
> 1)
1624 * Sole queue user, allow bigger slice
1630 * Async queues must wait a bit before being allowed dispatch.
1631 * We also ramp up the dispatch depth gradually for async IO,
1632 * based on the last sync IO we serviced
1634 if (!cfq_cfqq_sync(cfqq
) && cfqd
->cfq_latency
) {
1635 unsigned long last_sync
= jiffies
- cfqd
->last_end_sync_rq
;
1638 depth
= last_sync
/ cfqd
->cfq_slice
[1];
1639 if (!depth
&& !cfqq
->dispatched
)
1641 if (depth
< max_dispatch
)
1642 max_dispatch
= depth
;
1646 * If we're below the current max, allow a dispatch
1648 return cfqq
->dispatched
< max_dispatch
;
1652 * Dispatch a request from cfqq, moving them to the request queue
1655 static bool cfq_dispatch_request(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
1659 BUG_ON(RB_EMPTY_ROOT(&cfqq
->sort_list
));
1661 if (!cfq_may_dispatch(cfqd
, cfqq
))
1665 * follow expired path, else get first next available
1667 rq
= cfq_check_fifo(cfqq
);
1672 * insert request into driver dispatch list
1674 cfq_dispatch_insert(cfqd
->queue
, rq
);
1676 if (!cfqd
->active_cic
) {
1677 struct cfq_io_context
*cic
= RQ_CIC(rq
);
1679 atomic_long_inc(&cic
->ioc
->refcount
);
1680 cfqd
->active_cic
= cic
;
1687 * Find the cfqq that we need to service and move a request from that to the
1690 static int cfq_dispatch_requests(struct request_queue
*q
, int force
)
1692 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
1693 struct cfq_queue
*cfqq
;
1695 if (!cfqd
->busy_queues
)
1698 if (unlikely(force
))
1699 return cfq_forced_dispatch(cfqd
);
1701 cfqq
= cfq_select_queue(cfqd
);
1706 * Dispatch a request from this cfqq, if it is allowed
1708 if (!cfq_dispatch_request(cfqd
, cfqq
))
1711 cfqq
->slice_dispatch
++;
1712 cfq_clear_cfqq_must_dispatch(cfqq
);
1715 * expire an async queue immediately if it has used up its slice. idle
1716 * queue always expire after 1 dispatch round.
1718 if (cfqd
->busy_queues
> 1 && ((!cfq_cfqq_sync(cfqq
) &&
1719 cfqq
->slice_dispatch
>= cfq_prio_to_maxrq(cfqd
, cfqq
)) ||
1720 cfq_class_idle(cfqq
))) {
1721 cfqq
->slice_end
= jiffies
+ 1;
1722 cfq_slice_expired(cfqd
, 0);
1725 cfq_log_cfqq(cfqd
, cfqq
, "dispatched a request");
1730 * task holds one reference to the queue, dropped when task exits. each rq
1731 * in-flight on this queue also holds a reference, dropped when rq is freed.
1733 * queue lock must be held here.
1735 static void cfq_put_queue(struct cfq_queue
*cfqq
)
1737 struct cfq_data
*cfqd
= cfqq
->cfqd
;
1739 BUG_ON(atomic_read(&cfqq
->ref
) <= 0);
1741 if (!atomic_dec_and_test(&cfqq
->ref
))
1744 cfq_log_cfqq(cfqd
, cfqq
, "put_queue");
1745 BUG_ON(rb_first(&cfqq
->sort_list
));
1746 BUG_ON(cfqq
->allocated
[READ
] + cfqq
->allocated
[WRITE
]);
1747 BUG_ON(cfq_cfqq_on_rr(cfqq
));
1749 if (unlikely(cfqd
->active_queue
== cfqq
)) {
1750 __cfq_slice_expired(cfqd
, cfqq
, 0);
1751 cfq_schedule_dispatch(cfqd
);
1754 kmem_cache_free(cfq_pool
, cfqq
);
1758 * Must always be called with the rcu_read_lock() held
1761 __call_for_each_cic(struct io_context
*ioc
,
1762 void (*func
)(struct io_context
*, struct cfq_io_context
*))
1764 struct cfq_io_context
*cic
;
1765 struct hlist_node
*n
;
1767 hlist_for_each_entry_rcu(cic
, n
, &ioc
->cic_list
, cic_list
)
1772 * Call func for each cic attached to this ioc.
1775 call_for_each_cic(struct io_context
*ioc
,
1776 void (*func
)(struct io_context
*, struct cfq_io_context
*))
1779 __call_for_each_cic(ioc
, func
);
1783 static void cfq_cic_free_rcu(struct rcu_head
*head
)
1785 struct cfq_io_context
*cic
;
1787 cic
= container_of(head
, struct cfq_io_context
, rcu_head
);
1789 kmem_cache_free(cfq_ioc_pool
, cic
);
1790 elv_ioc_count_dec(cfq_ioc_count
);
1794 * CFQ scheduler is exiting, grab exit lock and check
1795 * the pending io context count. If it hits zero,
1796 * complete ioc_gone and set it back to NULL
1798 spin_lock(&ioc_gone_lock
);
1799 if (ioc_gone
&& !elv_ioc_count_read(cfq_ioc_count
)) {
1803 spin_unlock(&ioc_gone_lock
);
1807 static void cfq_cic_free(struct cfq_io_context
*cic
)
1809 call_rcu(&cic
->rcu_head
, cfq_cic_free_rcu
);
1812 static void cic_free_func(struct io_context
*ioc
, struct cfq_io_context
*cic
)
1814 unsigned long flags
;
1816 BUG_ON(!cic
->dead_key
);
1818 spin_lock_irqsave(&ioc
->lock
, flags
);
1819 radix_tree_delete(&ioc
->radix_root
, cic
->dead_key
);
1820 hlist_del_rcu(&cic
->cic_list
);
1821 spin_unlock_irqrestore(&ioc
->lock
, flags
);
1827 * Must be called with rcu_read_lock() held or preemption otherwise disabled.
1828 * Only two callers of this - ->dtor() which is called with the rcu_read_lock(),
1829 * and ->trim() which is called with the task lock held
1831 static void cfq_free_io_context(struct io_context
*ioc
)
1834 * ioc->refcount is zero here, or we are called from elv_unregister(),
1835 * so no more cic's are allowed to be linked into this ioc. So it
1836 * should be ok to iterate over the known list, we will see all cic's
1837 * since no new ones are added.
1839 __call_for_each_cic(ioc
, cic_free_func
);
1842 static void cfq_exit_cfqq(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
1844 struct cfq_queue
*__cfqq
, *next
;
1846 if (unlikely(cfqq
== cfqd
->active_queue
)) {
1847 __cfq_slice_expired(cfqd
, cfqq
, 0);
1848 cfq_schedule_dispatch(cfqd
);
1852 * If this queue was scheduled to merge with another queue, be
1853 * sure to drop the reference taken on that queue (and others in
1854 * the merge chain). See cfq_setup_merge and cfq_merge_cfqqs.
1856 __cfqq
= cfqq
->new_cfqq
;
1858 if (__cfqq
== cfqq
) {
1859 WARN(1, "cfqq->new_cfqq loop detected\n");
1862 next
= __cfqq
->new_cfqq
;
1863 cfq_put_queue(__cfqq
);
1867 cfq_put_queue(cfqq
);
1870 static void __cfq_exit_single_io_context(struct cfq_data
*cfqd
,
1871 struct cfq_io_context
*cic
)
1873 struct io_context
*ioc
= cic
->ioc
;
1875 list_del_init(&cic
->queue_list
);
1878 * Make sure key == NULL is seen for dead queues
1881 cic
->dead_key
= (unsigned long) cic
->key
;
1884 if (ioc
->ioc_data
== cic
)
1885 rcu_assign_pointer(ioc
->ioc_data
, NULL
);
1887 if (cic
->cfqq
[BLK_RW_ASYNC
]) {
1888 cfq_exit_cfqq(cfqd
, cic
->cfqq
[BLK_RW_ASYNC
]);
1889 cic
->cfqq
[BLK_RW_ASYNC
] = NULL
;
1892 if (cic
->cfqq
[BLK_RW_SYNC
]) {
1893 cfq_exit_cfqq(cfqd
, cic
->cfqq
[BLK_RW_SYNC
]);
1894 cic
->cfqq
[BLK_RW_SYNC
] = NULL
;
1898 static void cfq_exit_single_io_context(struct io_context
*ioc
,
1899 struct cfq_io_context
*cic
)
1901 struct cfq_data
*cfqd
= cic
->key
;
1904 struct request_queue
*q
= cfqd
->queue
;
1905 unsigned long flags
;
1907 spin_lock_irqsave(q
->queue_lock
, flags
);
1910 * Ensure we get a fresh copy of the ->key to prevent
1911 * race between exiting task and queue
1913 smp_read_barrier_depends();
1915 __cfq_exit_single_io_context(cfqd
, cic
);
1917 spin_unlock_irqrestore(q
->queue_lock
, flags
);
1922 * The process that ioc belongs to has exited, we need to clean up
1923 * and put the internal structures we have that belongs to that process.
1925 static void cfq_exit_io_context(struct io_context
*ioc
)
1927 call_for_each_cic(ioc
, cfq_exit_single_io_context
);
1930 static struct cfq_io_context
*
1931 cfq_alloc_io_context(struct cfq_data
*cfqd
, gfp_t gfp_mask
)
1933 struct cfq_io_context
*cic
;
1935 cic
= kmem_cache_alloc_node(cfq_ioc_pool
, gfp_mask
| __GFP_ZERO
,
1938 cic
->last_end_request
= jiffies
;
1939 INIT_LIST_HEAD(&cic
->queue_list
);
1940 INIT_HLIST_NODE(&cic
->cic_list
);
1941 cic
->dtor
= cfq_free_io_context
;
1942 cic
->exit
= cfq_exit_io_context
;
1943 elv_ioc_count_inc(cfq_ioc_count
);
1949 static void cfq_init_prio_data(struct cfq_queue
*cfqq
, struct io_context
*ioc
)
1951 struct task_struct
*tsk
= current
;
1954 if (!cfq_cfqq_prio_changed(cfqq
))
1957 ioprio_class
= IOPRIO_PRIO_CLASS(ioc
->ioprio
);
1958 switch (ioprio_class
) {
1960 printk(KERN_ERR
"cfq: bad prio %x\n", ioprio_class
);
1961 case IOPRIO_CLASS_NONE
:
1963 * no prio set, inherit CPU scheduling settings
1965 cfqq
->ioprio
= task_nice_ioprio(tsk
);
1966 cfqq
->ioprio_class
= task_nice_ioclass(tsk
);
1968 case IOPRIO_CLASS_RT
:
1969 cfqq
->ioprio
= task_ioprio(ioc
);
1970 cfqq
->ioprio_class
= IOPRIO_CLASS_RT
;
1972 case IOPRIO_CLASS_BE
:
1973 cfqq
->ioprio
= task_ioprio(ioc
);
1974 cfqq
->ioprio_class
= IOPRIO_CLASS_BE
;
1976 case IOPRIO_CLASS_IDLE
:
1977 cfqq
->ioprio_class
= IOPRIO_CLASS_IDLE
;
1979 cfq_clear_cfqq_idle_window(cfqq
);
1984 * keep track of original prio settings in case we have to temporarily
1985 * elevate the priority of this queue
1987 cfqq
->org_ioprio
= cfqq
->ioprio
;
1988 cfqq
->org_ioprio_class
= cfqq
->ioprio_class
;
1989 cfq_clear_cfqq_prio_changed(cfqq
);
1992 static void changed_ioprio(struct io_context
*ioc
, struct cfq_io_context
*cic
)
1994 struct cfq_data
*cfqd
= cic
->key
;
1995 struct cfq_queue
*cfqq
;
1996 unsigned long flags
;
1998 if (unlikely(!cfqd
))
2001 spin_lock_irqsave(cfqd
->queue
->queue_lock
, flags
);
2003 cfqq
= cic
->cfqq
[BLK_RW_ASYNC
];
2005 struct cfq_queue
*new_cfqq
;
2006 new_cfqq
= cfq_get_queue(cfqd
, BLK_RW_ASYNC
, cic
->ioc
,
2009 cic
->cfqq
[BLK_RW_ASYNC
] = new_cfqq
;
2010 cfq_put_queue(cfqq
);
2014 cfqq
= cic
->cfqq
[BLK_RW_SYNC
];
2016 cfq_mark_cfqq_prio_changed(cfqq
);
2018 spin_unlock_irqrestore(cfqd
->queue
->queue_lock
, flags
);
2021 static void cfq_ioc_set_ioprio(struct io_context
*ioc
)
2023 call_for_each_cic(ioc
, changed_ioprio
);
2024 ioc
->ioprio_changed
= 0;
2027 static void cfq_init_cfqq(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
,
2028 pid_t pid
, bool is_sync
)
2030 RB_CLEAR_NODE(&cfqq
->rb_node
);
2031 RB_CLEAR_NODE(&cfqq
->p_node
);
2032 INIT_LIST_HEAD(&cfqq
->fifo
);
2034 atomic_set(&cfqq
->ref
, 0);
2037 cfq_mark_cfqq_prio_changed(cfqq
);
2040 if (!cfq_class_idle(cfqq
))
2041 cfq_mark_cfqq_idle_window(cfqq
);
2042 cfq_mark_cfqq_sync(cfqq
);
2047 static struct cfq_queue
*
2048 cfq_find_alloc_queue(struct cfq_data
*cfqd
, bool is_sync
,
2049 struct io_context
*ioc
, gfp_t gfp_mask
)
2051 struct cfq_queue
*cfqq
, *new_cfqq
= NULL
;
2052 struct cfq_io_context
*cic
;
2055 cic
= cfq_cic_lookup(cfqd
, ioc
);
2056 /* cic always exists here */
2057 cfqq
= cic_to_cfqq(cic
, is_sync
);
2060 * Always try a new alloc if we fell back to the OOM cfqq
2061 * originally, since it should just be a temporary situation.
2063 if (!cfqq
|| cfqq
== &cfqd
->oom_cfqq
) {
2068 } else if (gfp_mask
& __GFP_WAIT
) {
2069 spin_unlock_irq(cfqd
->queue
->queue_lock
);
2070 new_cfqq
= kmem_cache_alloc_node(cfq_pool
,
2071 gfp_mask
| __GFP_ZERO
,
2073 spin_lock_irq(cfqd
->queue
->queue_lock
);
2077 cfqq
= kmem_cache_alloc_node(cfq_pool
,
2078 gfp_mask
| __GFP_ZERO
,
2083 cfq_init_cfqq(cfqd
, cfqq
, current
->pid
, is_sync
);
2084 cfq_init_prio_data(cfqq
, ioc
);
2085 cfq_log_cfqq(cfqd
, cfqq
, "alloced");
2087 cfqq
= &cfqd
->oom_cfqq
;
2091 kmem_cache_free(cfq_pool
, new_cfqq
);
2096 static struct cfq_queue
**
2097 cfq_async_queue_prio(struct cfq_data
*cfqd
, int ioprio_class
, int ioprio
)
2099 switch (ioprio_class
) {
2100 case IOPRIO_CLASS_RT
:
2101 return &cfqd
->async_cfqq
[0][ioprio
];
2102 case IOPRIO_CLASS_BE
:
2103 return &cfqd
->async_cfqq
[1][ioprio
];
2104 case IOPRIO_CLASS_IDLE
:
2105 return &cfqd
->async_idle_cfqq
;
2111 static struct cfq_queue
*
2112 cfq_get_queue(struct cfq_data
*cfqd
, bool is_sync
, struct io_context
*ioc
,
2115 const int ioprio
= task_ioprio(ioc
);
2116 const int ioprio_class
= task_ioprio_class(ioc
);
2117 struct cfq_queue
**async_cfqq
= NULL
;
2118 struct cfq_queue
*cfqq
= NULL
;
2121 async_cfqq
= cfq_async_queue_prio(cfqd
, ioprio_class
, ioprio
);
2126 cfqq
= cfq_find_alloc_queue(cfqd
, is_sync
, ioc
, gfp_mask
);
2129 * pin the queue now that it's allocated, scheduler exit will prune it
2131 if (!is_sync
&& !(*async_cfqq
)) {
2132 atomic_inc(&cfqq
->ref
);
2136 atomic_inc(&cfqq
->ref
);
2141 * We drop cfq io contexts lazily, so we may find a dead one.
2144 cfq_drop_dead_cic(struct cfq_data
*cfqd
, struct io_context
*ioc
,
2145 struct cfq_io_context
*cic
)
2147 unsigned long flags
;
2149 WARN_ON(!list_empty(&cic
->queue_list
));
2151 spin_lock_irqsave(&ioc
->lock
, flags
);
2153 BUG_ON(ioc
->ioc_data
== cic
);
2155 radix_tree_delete(&ioc
->radix_root
, (unsigned long) cfqd
);
2156 hlist_del_rcu(&cic
->cic_list
);
2157 spin_unlock_irqrestore(&ioc
->lock
, flags
);
2162 static struct cfq_io_context
*
2163 cfq_cic_lookup(struct cfq_data
*cfqd
, struct io_context
*ioc
)
2165 struct cfq_io_context
*cic
;
2166 unsigned long flags
;
2175 * we maintain a last-hit cache, to avoid browsing over the tree
2177 cic
= rcu_dereference(ioc
->ioc_data
);
2178 if (cic
&& cic
->key
== cfqd
) {
2184 cic
= radix_tree_lookup(&ioc
->radix_root
, (unsigned long) cfqd
);
2188 /* ->key must be copied to avoid race with cfq_exit_queue() */
2191 cfq_drop_dead_cic(cfqd
, ioc
, cic
);
2196 spin_lock_irqsave(&ioc
->lock
, flags
);
2197 rcu_assign_pointer(ioc
->ioc_data
, cic
);
2198 spin_unlock_irqrestore(&ioc
->lock
, flags
);
2206 * Add cic into ioc, using cfqd as the search key. This enables us to lookup
2207 * the process specific cfq io context when entered from the block layer.
2208 * Also adds the cic to a per-cfqd list, used when this queue is removed.
2210 static int cfq_cic_link(struct cfq_data
*cfqd
, struct io_context
*ioc
,
2211 struct cfq_io_context
*cic
, gfp_t gfp_mask
)
2213 unsigned long flags
;
2216 ret
= radix_tree_preload(gfp_mask
);
2221 spin_lock_irqsave(&ioc
->lock
, flags
);
2222 ret
= radix_tree_insert(&ioc
->radix_root
,
2223 (unsigned long) cfqd
, cic
);
2225 hlist_add_head_rcu(&cic
->cic_list
, &ioc
->cic_list
);
2226 spin_unlock_irqrestore(&ioc
->lock
, flags
);
2228 radix_tree_preload_end();
2231 spin_lock_irqsave(cfqd
->queue
->queue_lock
, flags
);
2232 list_add(&cic
->queue_list
, &cfqd
->cic_list
);
2233 spin_unlock_irqrestore(cfqd
->queue
->queue_lock
, flags
);
2238 printk(KERN_ERR
"cfq: cic link failed!\n");
2244 * Setup general io context and cfq io context. There can be several cfq
2245 * io contexts per general io context, if this process is doing io to more
2246 * than one device managed by cfq.
2248 static struct cfq_io_context
*
2249 cfq_get_io_context(struct cfq_data
*cfqd
, gfp_t gfp_mask
)
2251 struct io_context
*ioc
= NULL
;
2252 struct cfq_io_context
*cic
;
2254 might_sleep_if(gfp_mask
& __GFP_WAIT
);
2256 ioc
= get_io_context(gfp_mask
, cfqd
->queue
->node
);
2260 cic
= cfq_cic_lookup(cfqd
, ioc
);
2264 cic
= cfq_alloc_io_context(cfqd
, gfp_mask
);
2268 if (cfq_cic_link(cfqd
, ioc
, cic
, gfp_mask
))
2272 smp_read_barrier_depends();
2273 if (unlikely(ioc
->ioprio_changed
))
2274 cfq_ioc_set_ioprio(ioc
);
2280 put_io_context(ioc
);
2285 cfq_update_io_thinktime(struct cfq_data
*cfqd
, struct cfq_io_context
*cic
)
2287 unsigned long elapsed
= jiffies
- cic
->last_end_request
;
2288 unsigned long ttime
= min(elapsed
, 2UL * cfqd
->cfq_slice_idle
);
2290 cic
->ttime_samples
= (7*cic
->ttime_samples
+ 256) / 8;
2291 cic
->ttime_total
= (7*cic
->ttime_total
+ 256*ttime
) / 8;
2292 cic
->ttime_mean
= (cic
->ttime_total
+ 128) / cic
->ttime_samples
;
2296 cfq_update_io_seektime(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
,
2302 if (!cfqq
->last_request_pos
)
2304 else if (cfqq
->last_request_pos
< blk_rq_pos(rq
))
2305 sdist
= blk_rq_pos(rq
) - cfqq
->last_request_pos
;
2307 sdist
= cfqq
->last_request_pos
- blk_rq_pos(rq
);
2310 * Don't allow the seek distance to get too large from the
2311 * odd fragment, pagein, etc
2313 if (cfqq
->seek_samples
<= 60) /* second&third seek */
2314 sdist
= min(sdist
, (cfqq
->seek_mean
* 4) + 2*1024*1024);
2316 sdist
= min(sdist
, (cfqq
->seek_mean
* 4) + 2*1024*64);
2318 cfqq
->seek_samples
= (7*cfqq
->seek_samples
+ 256) / 8;
2319 cfqq
->seek_total
= (7*cfqq
->seek_total
+ (u64
)256*sdist
) / 8;
2320 total
= cfqq
->seek_total
+ (cfqq
->seek_samples
/2);
2321 do_div(total
, cfqq
->seek_samples
);
2322 cfqq
->seek_mean
= (sector_t
)total
;
2325 * If this cfqq is shared between multiple processes, check to
2326 * make sure that those processes are still issuing I/Os within
2327 * the mean seek distance. If not, it may be time to break the
2328 * queues apart again.
2330 if (cfq_cfqq_coop(cfqq
)) {
2331 if (CFQQ_SEEKY(cfqq
) && !cfqq
->seeky_start
)
2332 cfqq
->seeky_start
= jiffies
;
2333 else if (!CFQQ_SEEKY(cfqq
))
2334 cfqq
->seeky_start
= 0;
2339 * Disable idle window if the process thinks too long or seeks so much that
2343 cfq_update_idle_window(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
,
2344 struct cfq_io_context
*cic
)
2346 int old_idle
, enable_idle
;
2349 * Don't idle for async or idle io prio class
2351 if (!cfq_cfqq_sync(cfqq
) || cfq_class_idle(cfqq
))
2354 enable_idle
= old_idle
= cfq_cfqq_idle_window(cfqq
);
2356 if (!atomic_read(&cic
->ioc
->nr_tasks
) || !cfqd
->cfq_slice_idle
||
2357 (sample_valid(cfqq
->seek_samples
) && CFQQ_SEEKY(cfqq
)))
2359 else if (sample_valid(cic
->ttime_samples
)) {
2360 if (cic
->ttime_mean
> cfqd
->cfq_slice_idle
)
2366 if (old_idle
!= enable_idle
) {
2367 cfq_log_cfqq(cfqd
, cfqq
, "idle=%d", enable_idle
);
2369 cfq_mark_cfqq_idle_window(cfqq
);
2371 cfq_clear_cfqq_idle_window(cfqq
);
2376 * Check if new_cfqq should preempt the currently active queue. Return 0 for
2377 * no or if we aren't sure, a 1 will cause a preempt.
2380 cfq_should_preempt(struct cfq_data
*cfqd
, struct cfq_queue
*new_cfqq
,
2383 struct cfq_queue
*cfqq
;
2385 cfqq
= cfqd
->active_queue
;
2389 if (cfq_slice_used(cfqq
))
2392 if (cfq_class_idle(new_cfqq
))
2395 if (cfq_class_idle(cfqq
))
2398 if (cfqd
->serving_type
== SYNC_NOIDLE_WORKLOAD
2399 && new_cfqq
->service_tree
== cfqq
->service_tree
)
2403 * if the new request is sync, but the currently running queue is
2404 * not, let the sync request have priority.
2406 if (rq_is_sync(rq
) && !cfq_cfqq_sync(cfqq
))
2410 * So both queues are sync. Let the new request get disk time if
2411 * it's a metadata request and the current queue is doing regular IO.
2413 if (rq_is_meta(rq
) && !cfqq
->meta_pending
)
2417 * Allow an RT request to pre-empt an ongoing non-RT cfqq timeslice.
2419 if (cfq_class_rt(new_cfqq
) && !cfq_class_rt(cfqq
))
2422 if (!cfqd
->active_cic
|| !cfq_cfqq_wait_request(cfqq
))
2426 * if this request is as-good as one we would expect from the
2427 * current cfqq, let it preempt
2429 if (cfq_rq_close(cfqd
, cfqq
, rq
))
2436 * cfqq preempts the active queue. if we allowed preempt with no slice left,
2437 * let it have half of its nominal slice.
2439 static void cfq_preempt_queue(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
)
2441 cfq_log_cfqq(cfqd
, cfqq
, "preempt");
2442 cfq_slice_expired(cfqd
, 1);
2445 * Put the new queue at the front of the of the current list,
2446 * so we know that it will be selected next.
2448 BUG_ON(!cfq_cfqq_on_rr(cfqq
));
2450 cfq_service_tree_add(cfqd
, cfqq
, 1);
2452 cfqq
->slice_end
= 0;
2453 cfq_mark_cfqq_slice_new(cfqq
);
2457 * Called when a new fs request (rq) is added (to cfqq). Check if there's
2458 * something we should do about it
2461 cfq_rq_enqueued(struct cfq_data
*cfqd
, struct cfq_queue
*cfqq
,
2464 struct cfq_io_context
*cic
= RQ_CIC(rq
);
2468 cfqq
->meta_pending
++;
2470 cfq_update_io_thinktime(cfqd
, cic
);
2471 cfq_update_io_seektime(cfqd
, cfqq
, rq
);
2472 cfq_update_idle_window(cfqd
, cfqq
, cic
);
2474 cfqq
->last_request_pos
= blk_rq_pos(rq
) + blk_rq_sectors(rq
);
2476 if (cfqq
== cfqd
->active_queue
) {
2478 * Remember that we saw a request from this process, but
2479 * don't start queuing just yet. Otherwise we risk seeing lots
2480 * of tiny requests, because we disrupt the normal plugging
2481 * and merging. If the request is already larger than a single
2482 * page, let it rip immediately. For that case we assume that
2483 * merging is already done. Ditto for a busy system that
2484 * has other work pending, don't risk delaying until the
2485 * idle timer unplug to continue working.
2487 if (cfq_cfqq_wait_request(cfqq
)) {
2488 if (blk_rq_bytes(rq
) > PAGE_CACHE_SIZE
||
2489 cfqd
->busy_queues
> 1) {
2490 del_timer(&cfqd
->idle_slice_timer
);
2491 __blk_run_queue(cfqd
->queue
);
2493 cfq_mark_cfqq_must_dispatch(cfqq
);
2495 } else if (cfq_should_preempt(cfqd
, cfqq
, rq
)) {
2497 * not the active queue - expire current slice if it is
2498 * idle and has expired it's mean thinktime or this new queue
2499 * has some old slice time left and is of higher priority or
2500 * this new queue is RT and the current one is BE
2502 cfq_preempt_queue(cfqd
, cfqq
);
2503 __blk_run_queue(cfqd
->queue
);
2507 static void cfq_insert_request(struct request_queue
*q
, struct request
*rq
)
2509 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
2510 struct cfq_queue
*cfqq
= RQ_CFQQ(rq
);
2512 cfq_log_cfqq(cfqd
, cfqq
, "insert_request");
2513 cfq_init_prio_data(cfqq
, RQ_CIC(rq
)->ioc
);
2515 rq_set_fifo_time(rq
, jiffies
+ cfqd
->cfq_fifo_expire
[rq_is_sync(rq
)]);
2516 list_add_tail(&rq
->queuelist
, &cfqq
->fifo
);
2519 cfq_rq_enqueued(cfqd
, cfqq
, rq
);
2523 * Update hw_tag based on peak queue depth over 50 samples under
2526 static void cfq_update_hw_tag(struct cfq_data
*cfqd
)
2528 struct cfq_queue
*cfqq
= cfqd
->active_queue
;
2530 if (rq_in_driver(cfqd
) > cfqd
->rq_in_driver_peak
)
2531 cfqd
->rq_in_driver_peak
= rq_in_driver(cfqd
);
2533 if (cfqd
->rq_queued
<= CFQ_HW_QUEUE_MIN
&&
2534 rq_in_driver(cfqd
) <= CFQ_HW_QUEUE_MIN
)
2538 * If active queue hasn't enough requests and can idle, cfq might not
2539 * dispatch sufficient requests to hardware. Don't zero hw_tag in this
2542 if (cfqq
&& cfq_cfqq_idle_window(cfqq
) &&
2543 cfqq
->dispatched
+ cfqq
->queued
[0] + cfqq
->queued
[1] <
2544 CFQ_HW_QUEUE_MIN
&& rq_in_driver(cfqd
) < CFQ_HW_QUEUE_MIN
)
2547 if (cfqd
->hw_tag_samples
++ < 50)
2550 if (cfqd
->rq_in_driver_peak
>= CFQ_HW_QUEUE_MIN
)
2555 cfqd
->hw_tag_samples
= 0;
2556 cfqd
->rq_in_driver_peak
= 0;
2559 static void cfq_completed_request(struct request_queue
*q
, struct request
*rq
)
2561 struct cfq_queue
*cfqq
= RQ_CFQQ(rq
);
2562 struct cfq_data
*cfqd
= cfqq
->cfqd
;
2563 const int sync
= rq_is_sync(rq
);
2567 cfq_log_cfqq(cfqd
, cfqq
, "complete");
2569 cfq_update_hw_tag(cfqd
);
2571 WARN_ON(!cfqd
->rq_in_driver
[sync
]);
2572 WARN_ON(!cfqq
->dispatched
);
2573 cfqd
->rq_in_driver
[sync
]--;
2576 if (cfq_cfqq_sync(cfqq
))
2577 cfqd
->sync_flight
--;
2580 RQ_CIC(rq
)->last_end_request
= now
;
2581 cfqd
->last_end_sync_rq
= now
;
2585 * If this is the active queue, check if it needs to be expired,
2586 * or if we want to idle in case it has no pending requests.
2588 if (cfqd
->active_queue
== cfqq
) {
2589 const bool cfqq_empty
= RB_EMPTY_ROOT(&cfqq
->sort_list
);
2591 if (cfq_cfqq_slice_new(cfqq
)) {
2592 cfq_set_prio_slice(cfqd
, cfqq
);
2593 cfq_clear_cfqq_slice_new(cfqq
);
2596 * If there are no requests waiting in this queue, and
2597 * there are other queues ready to issue requests, AND
2598 * those other queues are issuing requests within our
2599 * mean seek distance, give them a chance to run instead
2602 if (cfq_slice_used(cfqq
) || cfq_class_idle(cfqq
))
2603 cfq_slice_expired(cfqd
, 1);
2604 else if (cfqq_empty
&& !cfq_close_cooperator(cfqd
, cfqq
) &&
2605 sync
&& !rq_noidle(rq
))
2606 cfq_arm_slice_timer(cfqd
);
2609 if (!rq_in_driver(cfqd
))
2610 cfq_schedule_dispatch(cfqd
);
2614 * we temporarily boost lower priority queues if they are holding fs exclusive
2615 * resources. they are boosted to normal prio (CLASS_BE/4)
2617 static void cfq_prio_boost(struct cfq_queue
*cfqq
)
2619 if (has_fs_excl()) {
2621 * boost idle prio on transactions that would lock out other
2622 * users of the filesystem
2624 if (cfq_class_idle(cfqq
))
2625 cfqq
->ioprio_class
= IOPRIO_CLASS_BE
;
2626 if (cfqq
->ioprio
> IOPRIO_NORM
)
2627 cfqq
->ioprio
= IOPRIO_NORM
;
2630 * unboost the queue (if needed)
2632 cfqq
->ioprio_class
= cfqq
->org_ioprio_class
;
2633 cfqq
->ioprio
= cfqq
->org_ioprio
;
2637 static inline int __cfq_may_queue(struct cfq_queue
*cfqq
)
2639 if (cfq_cfqq_wait_request(cfqq
) && !cfq_cfqq_must_alloc_slice(cfqq
)) {
2640 cfq_mark_cfqq_must_alloc_slice(cfqq
);
2641 return ELV_MQUEUE_MUST
;
2644 return ELV_MQUEUE_MAY
;
2647 static int cfq_may_queue(struct request_queue
*q
, int rw
)
2649 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
2650 struct task_struct
*tsk
= current
;
2651 struct cfq_io_context
*cic
;
2652 struct cfq_queue
*cfqq
;
2655 * don't force setup of a queue from here, as a call to may_queue
2656 * does not necessarily imply that a request actually will be queued.
2657 * so just lookup a possibly existing queue, or return 'may queue'
2660 cic
= cfq_cic_lookup(cfqd
, tsk
->io_context
);
2662 return ELV_MQUEUE_MAY
;
2664 cfqq
= cic_to_cfqq(cic
, rw_is_sync(rw
));
2666 cfq_init_prio_data(cfqq
, cic
->ioc
);
2667 cfq_prio_boost(cfqq
);
2669 return __cfq_may_queue(cfqq
);
2672 return ELV_MQUEUE_MAY
;
2676 * queue lock held here
2678 static void cfq_put_request(struct request
*rq
)
2680 struct cfq_queue
*cfqq
= RQ_CFQQ(rq
);
2683 const int rw
= rq_data_dir(rq
);
2685 BUG_ON(!cfqq
->allocated
[rw
]);
2686 cfqq
->allocated
[rw
]--;
2688 put_io_context(RQ_CIC(rq
)->ioc
);
2690 rq
->elevator_private
= NULL
;
2691 rq
->elevator_private2
= NULL
;
2693 cfq_put_queue(cfqq
);
2697 static struct cfq_queue
*
2698 cfq_merge_cfqqs(struct cfq_data
*cfqd
, struct cfq_io_context
*cic
,
2699 struct cfq_queue
*cfqq
)
2701 cfq_log_cfqq(cfqd
, cfqq
, "merging with queue %p", cfqq
->new_cfqq
);
2702 cic_set_cfqq(cic
, cfqq
->new_cfqq
, 1);
2703 cfq_mark_cfqq_coop(cfqq
->new_cfqq
);
2704 cfq_put_queue(cfqq
);
2705 return cic_to_cfqq(cic
, 1);
2708 static int should_split_cfqq(struct cfq_queue
*cfqq
)
2710 if (cfqq
->seeky_start
&&
2711 time_after(jiffies
, cfqq
->seeky_start
+ CFQQ_COOP_TOUT
))
2717 * Returns NULL if a new cfqq should be allocated, or the old cfqq if this
2718 * was the last process referring to said cfqq.
2720 static struct cfq_queue
*
2721 split_cfqq(struct cfq_io_context
*cic
, struct cfq_queue
*cfqq
)
2723 if (cfqq_process_refs(cfqq
) == 1) {
2724 cfqq
->seeky_start
= 0;
2725 cfqq
->pid
= current
->pid
;
2726 cfq_clear_cfqq_coop(cfqq
);
2730 cic_set_cfqq(cic
, NULL
, 1);
2731 cfq_put_queue(cfqq
);
2735 * Allocate cfq data structures associated with this request.
2738 cfq_set_request(struct request_queue
*q
, struct request
*rq
, gfp_t gfp_mask
)
2740 struct cfq_data
*cfqd
= q
->elevator
->elevator_data
;
2741 struct cfq_io_context
*cic
;
2742 const int rw
= rq_data_dir(rq
);
2743 const bool is_sync
= rq_is_sync(rq
);
2744 struct cfq_queue
*cfqq
;
2745 unsigned long flags
;
2747 might_sleep_if(gfp_mask
& __GFP_WAIT
);
2749 cic
= cfq_get_io_context(cfqd
, gfp_mask
);
2751 spin_lock_irqsave(q
->queue_lock
, flags
);
2757 cfqq
= cic_to_cfqq(cic
, is_sync
);
2758 if (!cfqq
|| cfqq
== &cfqd
->oom_cfqq
) {
2759 cfqq
= cfq_get_queue(cfqd
, is_sync
, cic
->ioc
, gfp_mask
);
2760 cic_set_cfqq(cic
, cfqq
, is_sync
);
2763 * If the queue was seeky for too long, break it apart.
2765 if (cfq_cfqq_coop(cfqq
) && should_split_cfqq(cfqq
)) {
2766 cfq_log_cfqq(cfqd
, cfqq
, "breaking apart cfqq");
2767 cfqq
= split_cfqq(cic
, cfqq
);
2773 * Check to see if this queue is scheduled to merge with
2774 * another, closely cooperating queue. The merging of
2775 * queues happens here as it must be done in process context.
2776 * The reference on new_cfqq was taken in merge_cfqqs.
2779 cfqq
= cfq_merge_cfqqs(cfqd
, cic
, cfqq
);
2782 cfqq
->allocated
[rw
]++;
2783 atomic_inc(&cfqq
->ref
);
2785 spin_unlock_irqrestore(q
->queue_lock
, flags
);
2787 rq
->elevator_private
= cic
;
2788 rq
->elevator_private2
= cfqq
;
2793 put_io_context(cic
->ioc
);
2795 cfq_schedule_dispatch(cfqd
);
2796 spin_unlock_irqrestore(q
->queue_lock
, flags
);
2797 cfq_log(cfqd
, "set_request fail");
2801 static void cfq_kick_queue(struct work_struct
*work
)
2803 struct cfq_data
*cfqd
=
2804 container_of(work
, struct cfq_data
, unplug_work
);
2805 struct request_queue
*q
= cfqd
->queue
;
2807 spin_lock_irq(q
->queue_lock
);
2808 __blk_run_queue(cfqd
->queue
);
2809 spin_unlock_irq(q
->queue_lock
);
2813 * Timer running if the active_queue is currently idling inside its time slice
2815 static void cfq_idle_slice_timer(unsigned long data
)
2817 struct cfq_data
*cfqd
= (struct cfq_data
*) data
;
2818 struct cfq_queue
*cfqq
;
2819 unsigned long flags
;
2822 cfq_log(cfqd
, "idle timer fired");
2824 spin_lock_irqsave(cfqd
->queue
->queue_lock
, flags
);
2826 cfqq
= cfqd
->active_queue
;
2831 * We saw a request before the queue expired, let it through
2833 if (cfq_cfqq_must_dispatch(cfqq
))
2839 if (cfq_slice_used(cfqq
))
2843 * only expire and reinvoke request handler, if there are
2844 * other queues with pending requests
2846 if (!cfqd
->busy_queues
)
2850 * not expired and it has a request pending, let it dispatch
2852 if (!RB_EMPTY_ROOT(&cfqq
->sort_list
))
2856 cfq_slice_expired(cfqd
, timed_out
);
2858 cfq_schedule_dispatch(cfqd
);
2860 spin_unlock_irqrestore(cfqd
->queue
->queue_lock
, flags
);
2863 static void cfq_shutdown_timer_wq(struct cfq_data
*cfqd
)
2865 del_timer_sync(&cfqd
->idle_slice_timer
);
2866 cancel_work_sync(&cfqd
->unplug_work
);
2869 static void cfq_put_async_queues(struct cfq_data
*cfqd
)
2873 for (i
= 0; i
< IOPRIO_BE_NR
; i
++) {
2874 if (cfqd
->async_cfqq
[0][i
])
2875 cfq_put_queue(cfqd
->async_cfqq
[0][i
]);
2876 if (cfqd
->async_cfqq
[1][i
])
2877 cfq_put_queue(cfqd
->async_cfqq
[1][i
]);
2880 if (cfqd
->async_idle_cfqq
)
2881 cfq_put_queue(cfqd
->async_idle_cfqq
);
2884 static void cfq_exit_queue(struct elevator_queue
*e
)
2886 struct cfq_data
*cfqd
= e
->elevator_data
;
2887 struct request_queue
*q
= cfqd
->queue
;
2889 cfq_shutdown_timer_wq(cfqd
);
2891 spin_lock_irq(q
->queue_lock
);
2893 if (cfqd
->active_queue
)
2894 __cfq_slice_expired(cfqd
, cfqd
->active_queue
, 0);
2896 while (!list_empty(&cfqd
->cic_list
)) {
2897 struct cfq_io_context
*cic
= list_entry(cfqd
->cic_list
.next
,
2898 struct cfq_io_context
,
2901 __cfq_exit_single_io_context(cfqd
, cic
);
2904 cfq_put_async_queues(cfqd
);
2906 spin_unlock_irq(q
->queue_lock
);
2908 cfq_shutdown_timer_wq(cfqd
);
2913 static void *cfq_init_queue(struct request_queue
*q
)
2915 struct cfq_data
*cfqd
;
2918 cfqd
= kmalloc_node(sizeof(*cfqd
), GFP_KERNEL
| __GFP_ZERO
, q
->node
);
2922 for (i
= 0; i
< 2; ++i
)
2923 for (j
= 0; j
< 3; ++j
)
2924 cfqd
->service_trees
[i
][j
] = CFQ_RB_ROOT
;
2925 cfqd
->service_tree_idle
= CFQ_RB_ROOT
;
2928 * Not strictly needed (since RB_ROOT just clears the node and we
2929 * zeroed cfqd on alloc), but better be safe in case someone decides
2930 * to add magic to the rb code
2932 for (i
= 0; i
< CFQ_PRIO_LISTS
; i
++)
2933 cfqd
->prio_trees
[i
] = RB_ROOT
;
2936 * Our fallback cfqq if cfq_find_alloc_queue() runs into OOM issues.
2937 * Grab a permanent reference to it, so that the normal code flow
2938 * will not attempt to free it.
2940 cfq_init_cfqq(cfqd
, &cfqd
->oom_cfqq
, 1, 0);
2941 atomic_inc(&cfqd
->oom_cfqq
.ref
);
2943 INIT_LIST_HEAD(&cfqd
->cic_list
);
2947 init_timer(&cfqd
->idle_slice_timer
);
2948 cfqd
->idle_slice_timer
.function
= cfq_idle_slice_timer
;
2949 cfqd
->idle_slice_timer
.data
= (unsigned long) cfqd
;
2951 INIT_WORK(&cfqd
->unplug_work
, cfq_kick_queue
);
2953 cfqd
->cfq_quantum
= cfq_quantum
;
2954 cfqd
->cfq_fifo_expire
[0] = cfq_fifo_expire
[0];
2955 cfqd
->cfq_fifo_expire
[1] = cfq_fifo_expire
[1];
2956 cfqd
->cfq_back_max
= cfq_back_max
;
2957 cfqd
->cfq_back_penalty
= cfq_back_penalty
;
2958 cfqd
->cfq_slice
[0] = cfq_slice_async
;
2959 cfqd
->cfq_slice
[1] = cfq_slice_sync
;
2960 cfqd
->cfq_slice_async_rq
= cfq_slice_async_rq
;
2961 cfqd
->cfq_slice_idle
= cfq_slice_idle
;
2962 cfqd
->cfq_latency
= 1;
2964 cfqd
->last_end_sync_rq
= jiffies
;
2968 static void cfq_slab_kill(void)
2971 * Caller already ensured that pending RCU callbacks are completed,
2972 * so we should have no busy allocations at this point.
2975 kmem_cache_destroy(cfq_pool
);
2977 kmem_cache_destroy(cfq_ioc_pool
);
2980 static int __init
cfq_slab_setup(void)
2982 cfq_pool
= KMEM_CACHE(cfq_queue
, 0);
2986 cfq_ioc_pool
= KMEM_CACHE(cfq_io_context
, 0);
2997 * sysfs parts below -->
3000 cfq_var_show(unsigned int var
, char *page
)
3002 return sprintf(page
, "%d\n", var
);
3006 cfq_var_store(unsigned int *var
, const char *page
, size_t count
)
3008 char *p
= (char *) page
;
3010 *var
= simple_strtoul(p
, &p
, 10);
3014 #define SHOW_FUNCTION(__FUNC, __VAR, __CONV) \
3015 static ssize_t __FUNC(struct elevator_queue *e, char *page) \
3017 struct cfq_data *cfqd = e->elevator_data; \
3018 unsigned int __data = __VAR; \
3020 __data = jiffies_to_msecs(__data); \
3021 return cfq_var_show(__data, (page)); \
3023 SHOW_FUNCTION(cfq_quantum_show
, cfqd
->cfq_quantum
, 0);
3024 SHOW_FUNCTION(cfq_fifo_expire_sync_show
, cfqd
->cfq_fifo_expire
[1], 1);
3025 SHOW_FUNCTION(cfq_fifo_expire_async_show
, cfqd
->cfq_fifo_expire
[0], 1);
3026 SHOW_FUNCTION(cfq_back_seek_max_show
, cfqd
->cfq_back_max
, 0);
3027 SHOW_FUNCTION(cfq_back_seek_penalty_show
, cfqd
->cfq_back_penalty
, 0);
3028 SHOW_FUNCTION(cfq_slice_idle_show
, cfqd
->cfq_slice_idle
, 1);
3029 SHOW_FUNCTION(cfq_slice_sync_show
, cfqd
->cfq_slice
[1], 1);
3030 SHOW_FUNCTION(cfq_slice_async_show
, cfqd
->cfq_slice
[0], 1);
3031 SHOW_FUNCTION(cfq_slice_async_rq_show
, cfqd
->cfq_slice_async_rq
, 0);
3032 SHOW_FUNCTION(cfq_low_latency_show
, cfqd
->cfq_latency
, 0);
3033 #undef SHOW_FUNCTION
3035 #define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV) \
3036 static ssize_t __FUNC(struct elevator_queue *e, const char *page, size_t count) \
3038 struct cfq_data *cfqd = e->elevator_data; \
3039 unsigned int __data; \
3040 int ret = cfq_var_store(&__data, (page), count); \
3041 if (__data < (MIN)) \
3043 else if (__data > (MAX)) \
3046 *(__PTR) = msecs_to_jiffies(__data); \
3048 *(__PTR) = __data; \
3051 STORE_FUNCTION(cfq_quantum_store
, &cfqd
->cfq_quantum
, 1, UINT_MAX
, 0);
3052 STORE_FUNCTION(cfq_fifo_expire_sync_store
, &cfqd
->cfq_fifo_expire
[1], 1,
3054 STORE_FUNCTION(cfq_fifo_expire_async_store
, &cfqd
->cfq_fifo_expire
[0], 1,
3056 STORE_FUNCTION(cfq_back_seek_max_store
, &cfqd
->cfq_back_max
, 0, UINT_MAX
, 0);
3057 STORE_FUNCTION(cfq_back_seek_penalty_store
, &cfqd
->cfq_back_penalty
, 1,
3059 STORE_FUNCTION(cfq_slice_idle_store
, &cfqd
->cfq_slice_idle
, 0, UINT_MAX
, 1);
3060 STORE_FUNCTION(cfq_slice_sync_store
, &cfqd
->cfq_slice
[1], 1, UINT_MAX
, 1);
3061 STORE_FUNCTION(cfq_slice_async_store
, &cfqd
->cfq_slice
[0], 1, UINT_MAX
, 1);
3062 STORE_FUNCTION(cfq_slice_async_rq_store
, &cfqd
->cfq_slice_async_rq
, 1,
3064 STORE_FUNCTION(cfq_low_latency_store
, &cfqd
->cfq_latency
, 0, 1, 0);
3065 #undef STORE_FUNCTION
3067 #define CFQ_ATTR(name) \
3068 __ATTR(name, S_IRUGO|S_IWUSR, cfq_##name##_show, cfq_##name##_store)
3070 static struct elv_fs_entry cfq_attrs
[] = {
3072 CFQ_ATTR(fifo_expire_sync
),
3073 CFQ_ATTR(fifo_expire_async
),
3074 CFQ_ATTR(back_seek_max
),
3075 CFQ_ATTR(back_seek_penalty
),
3076 CFQ_ATTR(slice_sync
),
3077 CFQ_ATTR(slice_async
),
3078 CFQ_ATTR(slice_async_rq
),
3079 CFQ_ATTR(slice_idle
),
3080 CFQ_ATTR(low_latency
),
3084 static struct elevator_type iosched_cfq
= {
3086 .elevator_merge_fn
= cfq_merge
,
3087 .elevator_merged_fn
= cfq_merged_request
,
3088 .elevator_merge_req_fn
= cfq_merged_requests
,
3089 .elevator_allow_merge_fn
= cfq_allow_merge
,
3090 .elevator_dispatch_fn
= cfq_dispatch_requests
,
3091 .elevator_add_req_fn
= cfq_insert_request
,
3092 .elevator_activate_req_fn
= cfq_activate_request
,
3093 .elevator_deactivate_req_fn
= cfq_deactivate_request
,
3094 .elevator_queue_empty_fn
= cfq_queue_empty
,
3095 .elevator_completed_req_fn
= cfq_completed_request
,
3096 .elevator_former_req_fn
= elv_rb_former_request
,
3097 .elevator_latter_req_fn
= elv_rb_latter_request
,
3098 .elevator_set_req_fn
= cfq_set_request
,
3099 .elevator_put_req_fn
= cfq_put_request
,
3100 .elevator_may_queue_fn
= cfq_may_queue
,
3101 .elevator_init_fn
= cfq_init_queue
,
3102 .elevator_exit_fn
= cfq_exit_queue
,
3103 .trim
= cfq_free_io_context
,
3105 .elevator_attrs
= cfq_attrs
,
3106 .elevator_name
= "cfq",
3107 .elevator_owner
= THIS_MODULE
,
3110 static int __init
cfq_init(void)
3113 * could be 0 on HZ < 1000 setups
3115 if (!cfq_slice_async
)
3116 cfq_slice_async
= 1;
3117 if (!cfq_slice_idle
)
3120 if (cfq_slab_setup())
3123 elv_register(&iosched_cfq
);
3128 static void __exit
cfq_exit(void)
3130 DECLARE_COMPLETION_ONSTACK(all_gone
);
3131 elv_unregister(&iosched_cfq
);
3132 ioc_gone
= &all_gone
;
3133 /* ioc_gone's update must be visible before reading ioc_count */
3137 * this also protects us from entering cfq_slab_kill() with
3138 * pending RCU callbacks
3140 if (elv_ioc_count_read(cfq_ioc_count
))
3141 wait_for_completion(&all_gone
);
3145 module_init(cfq_init
);
3146 module_exit(cfq_exit
);
3148 MODULE_AUTHOR("Jens Axboe");
3149 MODULE_LICENSE("GPL");
3150 MODULE_DESCRIPTION("Completely Fair Queueing IO scheduler");